1. Field
Apparatuses consistent with exemplary embodiments relate to blade devices, and more particularly, to blade assemblies.
2. Description of the Related Art
In the related art, a blade assembly may be used in various devices. For example, a blade assembly may be used in a compressor, a gas turbine, a steam turbine, and so on to generate an internal fluid flow by a rotation thereof. The blade assembly may be deformed during rotation thereof.
The blade assembly may include a rotor and a body portion connected to the rotor and rotating together with the rotor. The body portion may have a airfoil shape and may generate a fluid flow by rotating together with the rotor.
The body portion may rotate with a constant frequency and may be placed into a vacuum state when the rotation frequency becomes equal to a multiple of the resonance frequency.
When the body portion is in a vacuum state, parts thereof may deform/extend in a longitudinal direction. When the deformation occurs, an increased dynamic stress may act on the body portion which may result in breakage of the blade assembly or shortening of the lifespan thereof.
For example, the body portion can be subject to high levels of static arising from centrifugal and/or thermal forces resulting in low tolerance to dynamic stress levels. Many the gas/steam turbines and other compressor applications are subjected to frequent acceleration and deceleration. During these periods of acceleration or deceleration, the blade assembly may be momentarily subjected to high dynamic stresses while transitioning through resonance related conditions. When the blade assembly is subject to dynamic forces at or near the resonant frequency of the blade assembly, the amplitude of stress can readily build up to a point where fatigue related fractures occur. Under controlled test conditions, fatigue related fractures can occur after only a few seconds of operation due to dynamic stress associated with a blade resonance.
To attenuate the level of dynamic stresses in the blade assembly, various damping mechanisms have been introduced. For example, damping in the airfoil and/or airfoil to disk connection acts to reduce the level of dynamic stress at or near resonance conditions. The methods of the related art to introduce damping into the blade assembly can lead to wear and stress concentrations (lacing wires) fretting (contact zone mechanisms) and/or introduce damping at non-ideal locations.